1. Field of the Invention
The present invention relates to a circuit board connector and a board using this connector. More particularly, the invention relates to a circuit board connector mounted on a printed circuit board and a board using the connector.
2. Related Background Art
Traditionally, there has been known a circuit board connector mounted on a printing circuit board. A connector of such kind comprises a unit of male connector in which a plurality of connector pins are provided on the printed circuit board, and female connector which serves to secure an electrical conductivity for the male connector to prevent them from being fallen off. For this circuit board connector, there are typically a straight type in which the connector pins are planted on the surface of a mounting board almost vertically, and an edge type in which the connector pins are bent at right angles in the middle so that they are provided substantially in parallel with the surface of the mounting board.
Now, the description will be made briefly of a conventional straight type circuit board connector. FIG. 26 is a front view illustrating a conventional circuit board connector. In FIG. 26, the circuit board connector comprises a male connector portion 120 and a female connector portion 121 as a unit of one set. In the female connector portion 121, the connector terminals 124 represented by broken lines to which single lines 123 or flat cables (not shown) are connected are incorporated, and the electrical conductivity is implemented between each of the connector terminals 124 and connector pins 1 by the contacting force generated by the resilient deformation of the resilient portion of the connector terminals 124 when coupled with the connector pins 1. There are various types in practical use.
Also, the male connector portion 120 are provided with all the connector pins 1 almost vertically on the mounting surface of a circuit board 7. Therefore, the connector pins 1 are integrally formed with or pressed into a holder member 122 made of resin in advance, and after the end portions 1a of the connector pins 1 are inserted into the land holes of the circuit patterns on the surface of the circuit board 7, the integrated member is passed through a soldering flow tank or the like to form soldering portions 8 at once, thus performing the so-called soldering.
To the male connector portions 120 thus provided, the female connector portions 121 are pressed in detachably for use as a connector.
Particularly, when the male connector portions 120 in the circuit board connector are mounted, the temperatures of the circuit board 7 and the holder member 122 are considerably elevated, because the temperature at which the solder is solidified after the termination of the soldering is as high as one hundred and tens centigrade (.degree.C.).
After that, the circuit board 7 and holder member 122 which have been expanded by thermal expansion in the direction indicated by an arrow X in FIG. 26 are contracted in the direction indicated by an arrow Y while getting to the equilibrium state to the room temperature. At this juncture, however, a difference in amount of the contraction occurs due to the materials used, shapes, dimentions, and the like of the circuit board 7 and holder member 122.
Furthermore, the resin circuit board 7 and holder member 122 are of water absorptive, resulting in a more difference in the amounts of the contraction by the expansion or contraction by moisture and the difference in the storage periods.
Now, FIG. 27 is a microscopic photographing view illustrating the breaking part of the end 1a of the connector pin 1 structured as shown in FIG. 26. This is the result of an observation and recording of a crack K which is generated subsequent to the solidification of the solder 8 after the pin has been inserted into the land 7a of the circuit board 7. This crack K has reached as far as approximatly a half of the circumference of the connector pin 1, and the soldering is effectuated only by the remaining portion of another half of the circumference. This crack K is conspicuous particularly when the number of the connector pins is great. Conventionally, in order to prevent this, a method is adopted to separate the holder member 122 if many numbers of the connector pins should be provided.
It has been vertified that such crack K is generated due to the difference in the amount of the contraction of the above-mentioned circuit board 7 and holder member 122, further, there is a problem that the crack K brings upon a conductivity deficiency eventually because the crack K further propagates due to an external force, vibration, or changes in temperature and moisture (-10.degree. to 85.degree. C.) when the connector is used or stored as an electrical product.
Meanwhile, FIGS. 28A through 28C are views showing the processes in the conventional soldering flow and FIG. 28D illustrates the generation of a damage that the land 7b is peeled off when the female connector portion 30 is fitted onto the connector pin 1 which has been soldered in the processes shown in FIGS. 28A through 28C.
In other words, in FIG. 28A, the connector pin 1 integrally formed with the male connector 120 is inserted into the hole of the land portion 7b of the board 7. Then, when the integrated member is processed in a soldering flow equipment, there occurs a gap G as shown in FIG. 28B because the connector pin 1 which has been integrally formed with male connector portion 120 is raised from the board 7 by the flow of solder 8. Subsequently, after having waited for the solder to be solidified in the process shown in FIG. 28C, the female connector portion 30 is fitted as in FIG. 28D. Then, there encountered a problem in this process that the land 7b is peeled off from the board 1 at least by the amount equal to the gap G.
Also, the conventional connector is of rigid body in which the connector pins are integrally formed with resin, and there is no flexibility when it is mounted on a board. In addition, if the connector is mounted near a heat generating component such as a heating element or a motor, it is directly affected by heat. Hence, a problem happens that the electrical circuit between the board and the connector pins are broken and its function is disabled eventually.
Further, if a voltage is applied from a high voltage source to the connector pins in the circuit board as shown in FIG. 28, there is a problem that a discharge takes place between the pins if the interval between them is narrow.
Now, FIG. 29 is a view illustrating a copying machine (image formation apparatus) as an example of an apparatus using the connectors.
In FIG. 29, a reference mark a designates a case for the main body of the apparatus; b, a manuscript cover; c, an operation panel; d, a circuit board; and e, a transformer mounted on the circuit board d. Also, in the vicinity of the circuit board d, a motor f and other heat generating elements are arranged. A portion g surrounded by a circle represents a connector connected to the circuit board d. Inside the above-mentioned copying machine, an exposure unit, a development unit, a transfer unit, a photosensitive drum unit, sheet feed and exhaust unit, and the like are incorporated. For each of the units, a motor is arranged as a power source. For the smooth operation of each unit, particularly the development unit or the like, of a copying machine of the kind, heat is being added, and in the case of a machine in which the transformer, motor, and other heat generating elements are incorporated as in this example, there occur such problems as described above if the connector and circuit board are arranged in a close vicinity of those heat generating elements.